This invention relates to a bone fixing pin which is for use in fixation in osteosynthese, fixation after osteotomy, fixation of a transplantation bone, arthrodesis, complement, or supporting in an orthopedical and the like areas. The invention relates more concretely to a bone fixing pin which is for use in restoration of fracture portions, such as fixation of fractures of a distal end of humerus, a proximal end of humerus, a distal end of forearm bone, clavicule bone""s of digits, and the like, fixation after osteotomy in hallux valgus, rotational acetabular osteotomy, high tibial osteotomy, and the like, fixation of a bone graft (ilium, etc), arthrodesis in polyarthritis rheumatica chronica, arthrodesis in osteoarthritis deformans, and the like, supporting in fracture of a remote end of the radius, and complement or supporting in therapy of osteoporosis.
When fixation in osteosynthese, fixation after osteotomy, fixation of a transplantation bone, arthrodesis, and so on are carried out in an orthopedical and the like areas, generally employed are methods in which fixation is completed by the use of a metallic implant, such as a screw, a plate, a pin, and a wire, after provisionally fixing a plurality of bone fragments by inserting metallic pin and a metallic wire into the bone fragments to be thereby supported. In these methods, when the metallic pin is used as an implant, the metallic pin must be extracted therefrom by carrying out an extracting operation after bone assimilation. Due to a re-admission to a hospital and a re-operation for extracting the pin, there are problems that QOL (Quality of Life) is reduced and that increase of medical treatment cost is caused. Further, there is a danger of re-fracture, when the pin is extracted therefrom.
Accordingly, a pin which is not required to be extracted after bone assimilation has been used by using such a bio-absorptive polymer as divided gradually in an organism and eliminated after a certain period has passed as a material of a pin. Namely, in order to use this pin, at first, a metallic pin, such as a kirschner steel wire, of which a head is processed to be able to cut a bone is driven into a desirable position, so that bone fragments are provisionally fixed to each other. Next, a perforation is made at the other position by the use of a drill, and a bone fixing pin consisting of the bio-absorptive polymer is pushed into the perforation.
However, in a case of using such a pin, a perforation which dose not attribute to junction of the bone fragments to each other must be made, when the metallic pin for provisional fixation such as kirschner steel wire, is driven thereinto. Further, on a practical use, the metallic pin for provisional fixation is often driven into a position which is the most desirable for restoration and fixation of the bone fragments. This causes a problem that the main bone fixing pin consisting of bio-absorptive polymer is inevitably driven into a next desirable position other than the most desirable position.
Under these circumstances, a proposal is made about a bone fixing pin which is consisting of the bio-absorptive polymer and which can be driven into the most desirable position for the fixation of the bone fragments to each other, since it is not required to fix the bone fragments provisionally to each other by the use of a metallic pin therebefore. Further, in the proposal, a perforation can be made into a bone by this bone fixing pin itself without independently using a drill (See an official gazette of unexamined Japanese Patent Publication Hei 2-63450).
Namely, the bone fixing pin disclosed in the official gazette of unexamined Japanese Patent Publication Hei 2-63450 has a constitution in which a perforating section having a drill is joined to a cylindrical pin body section made from polymeric material. Further, the perforating section having the drill is formed to have a cylindrical shape. On the other hand, the pin body section is formed to have a taper enlarging the diameter thereof toward the direction opposite to that the pin body section is pushed thereinto. Besides, poly-dioxanone is disclosed in the official gazette as a preferable absorptive polymer.
However, in the bone fixing pin disclosed in the above-mentioned official gazette, the pin body section has the taper, so that loose of the pin body section is readily caused to occur within a perforation which is made by the perforating section having the drill. Further, since the pin body section has the taper, strength never become uniform over the whole of the pin body section, in other words, over the whole of a bone-joined portion. In addition, since the bone fixing pin has the taper enlarging the diameter thereof toward the direction opposite to that the pin body section is pushed thereinto, a considerably large strength must be added to make the pin body section be pushed thereinto. A special instrument for the purpose thereof must be prepared. Furthermore, as the poly-dioxanone used as a material for the pin body section has a comparatively small strength, the poly-dioxanone cannot be resistant to a large load. Moreover, the poly-dioxanone is divided comparatively fast in an organism. Accordingly, this bone fixing pin has a problem that applicable portions are restricted to bone""s of digits or the like.
The present invention solves the aforesaid problems of the conventional bone fixing pin. It is therefore an object of the present invention to provide a bone fixing pin, which is not required to be extracted therefrom even after bone assimilation, which can readily and smoothly be pushed into the most desirable position for fixation of the bone fragments to each other with the bone fixing pin making a perforation into the bone by itself, in which loose of the bone fixing pin is never caused to occur within the perforation thereby made, and for which applicable portions are increased.
It is yet another object of the present invention to provide use of a bone fixing pin, that is a therapy of osteoporosis.
It is further object of the present invention to provide a bone fixing pin to which roentgenography can be applied.
In order to achieve the above objects, a bone fixing pin of the present invention comprises a pin body section consisting of bio-absorptive high polymer, a perforating section which is joined to said pin body section and which has a drill at a head thereof, and is characterized in that at least said pin body section is formed to have the same thickness through the whole of the length direction thereof.
Namely, according to as aspect of the present invention, there is provided a bone fixing pin comprising: a pin body section consisting of bio-absorptive high polymer; a perforating section which is joined to said pin body section and which has a drill at a head thereof; characterized in that at least said pin body section is formed to have the same thickness through the whole of the length direction thereof.
Preferably, said perforating section is formed to have a cylindrical shape having a drill at a head thereof, and said pin body section is formed to have a cylindrical shape having the same diameter through the whole of the length direction thereof.
Further desirably, substantially whole of said bone fixing pin consisting of both said perforating section except for said drill at a head thereof and said pin body section is formed to have a cylindrical shape having the same diameter through the length direction thereof.
Herein, the bio-absorptive high polymer constituting said pin body section means a high polymeric material that is used as an implant material for operation and that is gradually absorbed in an organism and naturally eliminated after the operation.
Listed hereinunder can be used as the bio-absorptive high polymer.
At first, the following can be listed as synthetic high polymer.
polyester; poly-glycollic acid, poly-lactic acid, poly-L-lactic acid, poly-D-lactic acid, poly-D, L-lactic acid, poly-caprolacton, poly-dioxanone, poly-lacton, poly-(xcex1-malic acid), poly-(xcex2-malic acid), poly-(xcex1, xcex2-malic acid), etc.
polyamino acid; poly-glutamic acid, poly-aspartic acid, etc.
polycarbonate; poly-trimethylene carbonate, etc.
poly-(xcex1-cyanoacrylate); poly-(xcex1-cyanoacrylate), etc.
anhydride; poly-anhydride, etc.
ortho ester; poly-ortho ester, etc.
having nitrogen-phosphorus bond; poly-phosphazen, etc.
Further, the following can be listed as natural high polymer.
polyester; poly-hydroxybutyric acid, poly-hydroxyvaleric acid, etc.
polypeptide; gelatin, collagen, etc.
polyphosphate,
polyglycoside; starch, chitin, etc.
The above-listed high polymer or copolymer combining the above-listed high polymer together can be used as the bio-absorptive high polymeric material constituting the pin body section.
Further, composites having a high bio-affinity, such as hydroxyapatite, calcium phosphate, calcium hydrogenphosphate, calcium carbonate, calcium hydrogencarbonate, or the like may be added to said bio-absorptive high polymeric material as an additive. Accordingly, bio-affinity of the bone fixing pin can be improved. Further, hydroxyapatite, calcium phosphate, calcium hydrogenphosphate, calcium carbonate, calcium hydrogencarbonate, or the like is more hard to be transmitted by X-ray, compared with the bio-absorptive high polymer. By adding these, X-ray transmittance of the bio-absorptive high polymer can be reduced. It becomes easy to confirm a position, a condition of disappearance, and the like of the bone fixing pin by roentgenography after operation. Hydroxyapatite and calcium phosphate are preferable as an additive.
Preferably, the following can be listed as the bio-absorptive high polymer.
Namely, the following can be listed as synthetic high polymer.
polyester; poly-glycollic acid, poly-lactic acid, poly-L-lactic acid, poly-D-lactic acid, poly-D, L-lactic acid, poly-caprolacton, poly-dioxanone, poly-lacton, poly-(xcex1-malic acid), poly-(xcex2-malic acid), poly-(xcex1,xcex2-malic acid), etc.
polyamino acid; poly-glutamic acid, poly-aspartic acid, etc.
polycarbonate; poly-trimethylene carbonate, etc.
poly-(xcex1-cyanoacrylate); poly-(xcex1-cyanoacrylate), etc.
anhydride; poly-anhydride, etc.
ortho ester; poly-ortho ester, etc.
having nitrogen phosphorus bond; poly-phosphazen, etc.
Further, the following can be listed as natural high polymer.
polyester; poly-hydroxybutyric acid poly-hydroxyvaleric acid, etc.
polyphosphate;
polyglycoside; chitin, etc.
As a copolymer, a copolymer combining mainly polyester(for example, poly-glycollic acid, poly-lactic acid, poly-L-lactic acid, poly-caprolacton, poly-dioxanone) and subordinately the other, a copolymer including poly-L-lactic acid, a stereocomplex blending poly-L-lactic acid and poly-D-lactic acid, and the like are preferable.
Further, poly-L-lactic acid including hydroxyapatite, poly-L-lactic acid including calcium phosphate, a copolymer including poly-L-lactic acid, a stereocomplex blending poly-L-lactic acid and poly-D-lactic acid, and the like are also preferable.
In particular, poly-L-lactic acid, a copolymer including poly-L-lactic acid, a stereocomplex blending poly-L-lactic acid and poly-D-lactic acid, poly-L-lactic acid including hydroxyapatite are preferable.
Moreover, as a method of joining said pin body section and said perforating section, for example, a calling method, a screwing method, a hooking method, blinding method, and the like can be listed. Among them, calking method is desirable in respect of strength. Further, also in a method other than the calking method, in order to reinforce the joined portion, there is another method in which the joined portion is fixed by pressurizing therearound, after portions to be joined of said pin body section and said perforating section are interfit to each other.
In particular, in a case that poly-L-lactic acid or a copolymer including poly-L-lactic acid is used as a material of said pin body section, since the poly-L-lactic acid, and so on have a certain strength, the portion joined to the perforating section is easily worked. Thus, in the case, the method in which the joined portion is fixed by pressurizing therearound after portions to be joined of said pin body section and said perforating section are interfit to each other can be readily carried out.
By employing these methods of joining, it is not necessary to use an adhesive for joining the pin body section and the perforating section to each other. Accordingly, it is not dangerous that components of the adhesive remain in an organism, so that the bone fixing pin of the present invention can be safely used.